Control circuit



Aug. 11, 1931. c. P. STOCKER CONTROL CIRCUIT Filed July 11, 1930 INVENTOR I C. R STOC/(ER I 17% A TTORNE V Patented M11, 1931 UNITED STATES PATENT OFFICE;

01.0mm P. O! NEW YORK, N. Y, ABSIGNOB "1'0 3m TELEPHONE IlABOB-A- 150m INCORPORATED, 0] NEW YORK, N.-Y-. A CORPORATION OF NEW YORK oon'rnon cnwm Application fled m 11, mo. Serial :6. 467,288. I

This invention relates to electro-responsive devices and particularly to control of the responding interval of electro-magnetic devices such as relays.

It is an object of this invention to control the operation of circuits containing electro-res nsive devices, more particularly the operation of circuits in which the functioning of a relay in response to an applied signal is to be delayed.

v Several methods are available for controlling the delay in the response of a relay, some depending on the construction of the relay itself, others depending" on the characteristics of the circuits. with which the relay is associated. The present invention,

.which is of this latter general class, provides circuit means whereby the operation of a relay in response to control si nals may be regulated, so that the relay wi function at any predetermined time after signals are first applied, will hold its position as long as the, signals continue, and will return to its original condition at a predetermined time a ter the signals cease.

In accordance with applicants invention the relay which is to be operated is placed in the output circuit of a'space discharge device. Signals applied to the input of such a device would ordinarily cause an immediate change in the impedance of the device with a resultant change the output current passing through the relay; but means are provided whereby a change in the impedance of the tube produces on, a

control electrode in the discharge device a bias tending to oppose the change inimpedance caused by the input signals. The

ias set up by this action is gradual] re-' moved by means of a delay circuit an the output current finally assumes a value corres nding to the new conditions. At some time during this gradual change in output current, determined by the constants of the delay circuit and the adjustment of the relay, the latter mechanism 0 rates. A similar delayed action obtains w en signals cease, as the chan e in condition of the output circuit is again transmitted to the control electrode Where a gradually diminishing, opposing action is set up.

In the circuit used herein for purposes of illustration, the retro-action and delay are effected through a combination of resistance and capacit which controls the energy transferred rom the output circuit to affect a more sensitive part of the circuit. By use of such a combination, applicant is able to increase greatly the duration of the response interval and with a reduction in cost of apparatus.

The invention will be better understood by a consideration of the following detailed description, reference being made to the drawing, of which the single figure shows diagrammatically an embodiment a plied to an alarm circuit in a call-announcmg telephone exchange system.

In a call-announcing system several electrical channels are provided in each of which a spoken digit or letter is continuously repeated, and it is in connection with such a channel that an embodiment of the present invention will be described.

In the single figure of the drawing is shown one unit of the telephone exchange system more fully detailed in U. S. Patent 1,645,573, issued October 18, 1927, to H. M. Bascom. In each concentric circular channel on the transparent disc 1 is placed a fihn record 2 of a spoken numeral, which as the disc is rotated by motor 3 modulates the light passing from lamp 4 to photoelectric cell 5. The recorded numeral is thereby translated into equivalent electrical waves, which are then conducted to amplifer 6.

The output of the photoelectric cell amplifier 6 delivered to channel 7 is therefore a succession of speech signals equivalent to the vocal repetition of a particular numeral, and

it is to be utilized in a part of the telephone exchange not shown in the drawing nor .b'wt i to an understanding of this mvention.

.It is desirable to have an indication, as an audible-one, when the above described circuit fails to function, and for this purpose an alarm circuit is provided, comprising a bell 9 and batter 10 ada ted to be connected in operative re ation w encontact is closed by the release of an armature associated with relay winding 11. The action of the relay is controlled by the output current of a space discharge device 12 whose control circuit is connected to channel 7. Normall i. e., as long as the series of speech signa s is being generated, the relay is maintained in an operated position, as shown. Upon failure of these signals the output impedance of the discharge device increases, the current passing through the relay diminishes and the armature of the latter falls back to complete the alarm circuit.

In order to prevent the relay from releasing during the interval between called digits, which may be of the order of a quarter of a second, means to retard the action of the circuit are provided. These latter means are found in the combination of resistance 15, condenser 16 and condenser 17. The anode circuit resistor 18 also has a part in the action. 7

When a series of signals passes through channel 7 the signals are impressed by means of transformer 14 on the in ut circuit of s ace dischar e device 12, con ensers 16 and 1 in series s unting the signals around resistance 15. The negative grid bias afforded by the voltage drop across the resistance 19 in the filament circuit of the discharge device, is adjusted so that the latter device operates as a late circuit rectifier. That is, t e negative ias is made so large that id circuit rectification is negligible. Wit a sifgnal present then, the output impedance 0 the discharge device, and therefore the voltage dro across it, is substantially less than it is with no signal present.

The electrostatic charge on condenser 17 which is determined by the direct-current voltage drop across the discharge device, increases with the increase of this direct-current voltage dro that attends cessation of input signals. he circuit through which the charging current of the latter condenser, 17, flows includes resistance 15 and the parallel resistances 18 and R R representing the out ut impedance of the discharge device. lthough the primary purpose of the other condenser, 16, is to shunt the incoming si al around resistance 15, its charging current also has some effect on the action of the relay as will be explained hereinafter. It will be seen from the diagram that the direction of the charging current of condenser 17 in p through resistance 15 is such as to make e grid end of the resistance positive with respect to the filament end. The decrease in negative bias on the grid caused by this voltage drop tends to maintain the initial low impedance of the dischar e ,device and to kee relay 11 operated. charge on con enser 17 increases and the charging current gradually approaches zero, the voltage drop in resistance 15 also decreases and its counteracting eflect on the change in anode circuit impedance likewise gradually diminishes. Finally it becomes zero, the output im edance R, reaches a high value determined 3 the grid biasing drop in resistance 19, an the output current becomes constant at a relatively low level. At some instant during this interval the out ut current becomes too weak to hold the re ay,

and the latter releases. The length of time between cessation of signals and the release of the relay may be accurately controlled by proportioning the capacit of condenser 17 and the resistance of its c arging circuit, as these are factors determining the duration, or more precisely, the rate of decay, of the charging current.

A second armature and contact 25 asso ciated with relay winding 11 may be used for any desired purpose, such as to cause a second digit-calling channel to be substituted when the first one becomes inoperative.

No attempt has been made to set forth the relative proportions of the various elements comprlsin the circuits of Fig. 1,.inasmuch as consi erable latitude must be allowed for those variable factors such as the amplitude of the incoming signal, the characteristics of the dischar e device and the relay, and' the amount of elay required. In one particular case the capacity of condenser 17 was two microfarads, that of 16, a half a microfarad, the resistance of 15, a hundred thousand ohms, and that of 18, twenty-four thousand ohms.

It has been hereinbefore noted that with the the variation of anode circuit impedance,

condenser 16 also charges and discharges, part of the current passing through the relay and tending to delay its operation. This action occurs entirely In the output circuit and of itself would cause only a comparatively short delay in the operation of the relay. The advantages obtained by the present invention in utilizing a large amount of energy released by a change in output cir' cuit conditions to effect in control circuit conditions a change that can be considerably prolonged, is not present where the energy released is utilized directly in the apparatus to be controlled.

In the foregoing description the operation of the circuit after signals cease has been considered. Without going into detail, it is believed to be clear that when signals are first'impressed on the input terminals, the high impedance of the discharge device and the voltage drop across it tend to become low, discharge currents flow from condensers 16 an'd 17, respectively, that from the latter causing a decreasing negative drop to be created across resistance 15 in the grid circuit of the discharge device, the negative grid bias is thereby temporarlly increased, and the actuation of the anode circuit relay is delayed.

It is to be understood that the call announcer and alarm circuits are only adjuncts to an embodiment of the invention, and that various elements and circuit combinations for associating output and control circuits other than the particular ones disclosed are within the scope of the invention as defined by the following claims.

What is claimed is:

1. A space discharge device having impedance control means, input and output circuits associated with said device, an element responsive to the current in said output circuit, means associating said output circuit and said control means whereby theeffect ofinput signals on the action of said element is retarded.

2. A space discharge device having means for controlling the resistance of its discharge path, in ut and output circuits associated with sai device, and means associated with said controlling means and responsive to ourrent in said output circuit temporarily opposing the effect of input signals on said output current.

3. The combination with a space discharge device having an impedance control circuit and an out ut circuit, of means tending to produce su den changes in the output current, a circuit containing reactance connected to receive a portion of the variable component of said output current, and means to apply to said control circuit, a voltage from said reactance-containingl circuit which is initially large and gradua y diminishes, the direction of said voltage being such as to oppose the action giving rise to it.

4. The combination with a space discharge device having input, output and control circuits and whose direct current output impedance varies with the amplitude of signals applied to said input circuit, and an element controlled by the output current thereof, of a reactive circuit for translating the changes in output circuit conditionoccasioned by a change of input signal amplitude intoa gradually diminishin control circuit potential, retarding said 0 ange in said output circuit condition.

5. The combination with a current operated element and a condenser-resistance combination for timing the operation of said element, of a three-electrode space discharge device having its space path included in the device,

energizing circuit of said element and efl'ectively in shunt with said oondenser-resistance combination, the control circuit of said discharge device 'being connected to derive a voltage from a portion of said resistance condenser combination.

6. A rectifier comprising a space discharge a condenser whose potential is determined resistance in the charging circuit of said condenser, and means for controlling the output impedance of said device in accordance withthe voltage across said resistance.

7. In combination, a three-electrode space discharge rectifying device, a current-operated element in the output circuit thereof, a circuit associating the output and control electrodes of said device and conducting to said control electrode a gradually mg bias opposing the e ect on the conductivity of said rectifier of changes in the amplitude of an applied signal.

8, In combination, a three-electrode space discharge rectifyin device, a current-operated element energized by the out ut current thereof, a condenser adapts to v be charged in accordance with thev voltage across' the space path of said discharge vice, and a resistance common to the control circuit of said device and the charging cirby the output impedance thereof, a

cuit of said condenser for timing the operation of said element.

9. The combination for delaying the functioning of a current-o rated element comprisin a three-electrodh space discharge device a apted to operate as a plate circuit rectifier and having its space path included in the energizing circuit of said element, a circuit comprisin resistance and capacity ada ted to be 0 ar edv or discharged in accor ance with the c ange in the output im-' pedance of said rectifier, the biasin potential for the control electrode of said device being obtained in part from a point on said resistance-capacity circuit.

10. The combination with a current-operated element and a condenser-resistance combination for timing the operation of said element, of a three-electrode space discharge device having greater resistance to direct current when no signals are applied to its input circuit than when signals are present,

and having its space path eflectively in shunt with said condenser-resistance combination and included in series with an external resistance and the energizing circuit of said element, the potential of the control electrode of said discharge device being in part determined by its circuit connection with a point on said resistance condenser combination.

11.. The combination with a relay and a condenser-resistance combination for timing the operation of said relay, of a three-electrode space discharge device whose output impedance decreases as signals are applied to its in ut electrodes and whose space path is eflectively in shunt with said condenserresistance combination and in series with an external resistance and an energizin winding of said relay the control circuit 0 said discharge device being connected to derive a voltage from a part of said condenserresistance combination.

In witness whereof, I hereunto subscribe my name this 10th day of Jul 1930.

CLOSMAN P. S OCKER. 

